1. Field of the Invention
The present general inventive concept relates generally to an image processing apparatus and a control method thereof, and more particularly, to an image processing apparatus and a control method thereof, which can improve the picture quality of a scanned image.
2. Description of the Related Art
An image processing apparatus reads an image recorded on a page (or possibly two) of a manuscript by irradiating light onto the page(s) of the manuscript to obtain the displayed information. For example, an image processing apparatus may include a scanner, a facsimile, a multifunctional device that performs functions of the scanner and the facsimile through a single device, a document translator, a computer for CAD (computer aided design), a character recognizer, a digital copier and the like.
In order to read the manuscript, a scanning unit must move or the manuscript must move. An image processing apparatus, in which a scanning unit moves, will be referred to as a flat-bed scanning type image processing apparatus. Further, an image processing apparatus, in which the manuscript moves, will be referred to as a sheet-feed scanning type image processing apparatus.
The flat-bed scanning type image processing apparatus includes a flat glass, on which the manuscript is put, and a scanning unit provided on the rear surface of the flat glass. The scanning unit includes a light source for irradiating light onto the manuscript, a plurality of mirrors for reflecting an optical signal reflected from the manuscript, a lens to collect the optical signal reflected from the mirrors, and an image sensor for converting the optical signal, which is transferred from the lens, into an electrical signal. Further, the scanning unit can scan a book as well as a sheet of a paper similarly to a general copier.
In such an image processing apparatus, the manuscript makes intimate contact with the surface of the flat glass installed on the upper surface of the body of the image processing apparatus. Thus, the focal distance for image scanning of the manuscript is fixed on the surface of the flat glass, so that a clear image can be obtained.
As illustrated in FIG. 1, when the manuscript is a three-dimensional object such as a thick book, since not all areas of the two scanned pages of the manuscript make intimate contact with the flat glass (especially the areas around the binding, i.e. the vertical center), the focal distance relative to a scanning area is not uniform, and the focal distance between a lens and the center of the book is lengthened (is located farther from the lens). Thus, a clear image may not be obtained due to mis-focusing. In the case of the center region of the book, characters become dim gradually due to the misalignment of the focal distance.
In order to avoid such problems, Japanese Unexamined Patent Publication No. 2000-165608 discloses technology in which two flat glasses having manuscript thereon are inclined at a predetermined angle, and two scanning units corresponding to the two flat glasses are provided on the rear surfaces of the two flat glasses, so that clear images can be obtained by scanning the left and right parts of a book, respectively.
However, since two flat glasses and two scanning units must be provided, the construction of an image processing apparatus is complicated and costly.